MONACA, Pa. — President Donald Trump sought to take credit Tuesday for the construction of a major manufacturing facility in western Pennsylvania as he tries to reinvigorate supporters in the Rust Belt towns that sent him to the White House in 2016.

Trump visited Shell’s soon-to-be completed Pennsylvania Petrochemicals Complex, which will turn the area’s vast natural gas deposits into plastics. The facility, which critics claim will become the largest air polluter in western Pennsylvania, is being built in an area hungry for investment.

Speaking to a crowd of thousands of workers dressed in fluorescent orange and yellow vests, Trump said “This would have never happened without me and us.” In fact, Shell announced its plans to build the complex in 2012, when President Barack Obama was in office. A Shell spokesman said employees were paid for their time attending Trump’s remarks.

He used the official White House event as an opportunity to assail his would-be Democratic rivals, saying, “I don’t think they give a damn about Western Pennsylvania, do you?”

The focus is part of a continued push by the Trump administration to increase the economy’s dependence on fossil fuels in defiance of increasingly urgent warnings about climate change. And it’s an embrace of plastic at a time when the world is sounding alarms over its impact.

Trump’s appeals to blue-collar workers helped him win Beaver County, where the plant is located, by more than 18 percentage points in 2016, only to have voters turn to Democrats in 2018’s midterm elections. In one of a series of defeats that led to Republicans’ loss of the House, voters sent Democrat Conor Lamb to Congress after the prosperity promised by Trump’s tax cuts failed to materialize.

Today, Beaver County is still struggling to recover from the shuttering of steel plants in the 1980s that surged the unemployment rate to nearly 30%. Former mill towns like Aliquippa have seen their populations shrink, while Pittsburgh has lured major tech companies like Google and Uber, fueling an economic renaissance in a city that reliably votes Democratic.

Trump claimed that his steel and aluminum tariffs have saved the industries and that they are now “thriving,” exaggerating the recovery of the steel industry, particularly when it comes to jobs, which have largely followed pace with broader economic growth.

Trump took credit for the addition of 600,000 U.S. manufacturing jobs, but Labor Department figures show that roughly 500,000 factory jobs have been added since his presidency started.

The sector has also started to struggle this year as the administration intensified its trade war with China and factory production has declined. Pennsylvania has lost 5,600 manufacturing jobs so far this year, according to the Labor Department.

The region’s natural gas deposits had been seen, for a time, as its new road to prosperity, with drilling in the Marcellus Shale reservoir transforming Pennsylvania into the nation’s No. 2 natural gas state. But drops in the price of oil and gas caused the initial jobs boom from fracking to fizzle, leading companies like Shell to turn instead to plastics and so-called cracker plants — named after the process in which molecules are broken down at high heat, turning fracked ethane gas into one of the precursors for plastic.

The company was given massive tax breaks to build the petrochemicals complex, along with a $10 million site development grant, with local politicians eager to accommodate a multibillion-dollar construction project.

But “fracking for plastic” has drawn alarm from environmentalists and other activists, who warn of potential health and safety risks to nearby residents and bemoan the production of ever more plastic. There has been growing alarm over the sheer quantity of plastic on the planet, which has overwhelmed landfills, inundated bodies of water and permeated the deepest reaches of the ocean. Microplastics have also been found in the bodies of birds, fish, whales and people, with the health impacts largely unknown.

“Of all the things we could invest in, of all the things we should be prioritizing, of all the companies we should be giving our taxpayer money to, this seems like the worst of all worlds,” said David Masur, executive director of PennEnvironment, a statewide environmental advocacy organization, who called the project “a pretty big taxpayer boondoggle for a pretty dirty project.”

Trump defended the investment in plastics, claiming pollution in the ocean is “not our plastic.”

“It’s plastics that’s floating over in the ocean and the various oceans from other places,” he told reporters before boarding Air Force One.

A spokesman for the company, Ray Fisher, said Shell has “dedicated a great deal of time and resources” to ensure emissions from the plant meet or exceed local, state and federal requirements. “As designed, the project will actually help improve the local air shed as it relates to ozone and fine particulates,” he said.

The project currently has 5,000 construction workers. Once operational, however, the number of permanent employees at the site will shrink to 600.

But the area still faces other headwinds. The nearby Beaver Valley Power Station, a nuclear plant that has employed 850 people, has announced plans to close in 2021. And the Bruce Mansfield Power Plant, once the state’s largest coal-powered plant, announced Friday that it would close this fall, 19 months earlier than expected, at a cost of at least 200 jobs.